Electrically fired borehole gun



Sept. 22, 1942.

R. R. THOMPSON ELECTRICALLY FIRED BORE HOLE GUN 2 Sheets-Sheet 2 Filed March 17, 1959 Nw f3 wm. mw www um mm. mw mm.. ww w n s@ mm 2 mm mw w n 2% www MM mw E @Q QN INVENTOR.

.7J ATTORNEY.

Patented Sept. 22, 1942 ELEc'rmoALLY man onEnoLE GUN Robert R. Thompson, Houston, Tex., assignor to Standard Oil Development Company, a corporation of Delaware Application March 17, 1939, Serial No. 262,367

6 Claims. (Cl. 164-05) The present invention is directed to a gun per- .forator for use in boreholes and has particular reference to a ring circuit'thereior.

An object of thepresent invention is the provision of a gun perforator a-dapted to be iired electrically, the wiring of the firing circuit of which is arranged wholly on the exterior of the gun in a readily accessible manner.

An additional object of the present invention is the provision of a device of the character described having a tiring circuit so constructed that the bullets can be fired consecutively at any desired time interval by the application of a voltage which increases linearly as distinguished f from logarithmically with the.number of shots,

whereby, for a given number of shots, a smaller voltage range will be suiiicient.

Another object of the present invention is the provision of a gun perforator of the character described having a ring circuit operable on alternating or direct current and requiring only a single conductor cable in the borehole for operation;

An additional object of the present invention is the provision of a gun perforator of the character described in which the firing circuit is so arranged that the voltage applied is grounded behind each bullet in succession and this ground connection is broken upon the discharge ofthe bullet so as to make the voltage available for the firing of the next bullet.

Still another object of the present invention is the provision of a gun perforator of the character described in which the ilring mechanism has no moving parts. Further objects and advantages of the present invention will appear from the following detailed description of the accompanying drawings, in Which- Figure l isa Vertical section through a borehole in diagrammatic f orm showing the general assembly of a gun perforator in use;

Figure 2 is a detail View of a section of the gun barrel showing the exterior arrangement of the ring circuit; v A

Figure 3 is a-schematic illustration of the ring circuit; and

Figure 4 is a section along the line A-A oi Figure 2.

Referring to the drawings in detail, numeral designates a borehole provided with a casing 2, and illled with a duid, such as drilling mud,.3.

nions 8. The cable vcarries a conductor 9 which is connected through a conventional slip ring arrangement (not speciiilcally shown), to a conductor I0 at the surface which is connected to one terminal of a battery Ii, the other terminal of which is connected to a contact point I2 arranged to make periodic contact with contact members I3 mounted on a rotating switch I4,

the latter being connected to a yground electrode l I5 by a wire I6. It will be understood that any type switch may be employed,`a,simp1e hand switch being suiicient generally.

The gun 4 is providedwith a spiral groove Il in which is laid a wire i8 which is al continuation of conductor 9. Oiset from the spiral groove in intervals are cylindrical cavities i9 fitted with plugs 20. Each plug in turn has a central bore 2i in which is iixed a bullet 22 which is insulated from the plug by a layer of insulating material 23 which may be rubber or an artificial resin The inner end of the bullet has a circumferential flange 2li over which is fitted a rubber cap 25, secured in place by threaded ring 26. The plug is recessed and threaded at its inner end to receive the ilange 26, the cap 25 and the ring 26 in such a manner that when the bullet is ired the flange is sheared oi by the shoulder 2l in bore 2i. Plug 2Q is exteriorlyl threaded for engagement with the body of the gun barrel. Extending inwardly from cavity I9 is a smaller cavity 28 vwhich contains a powder can 29 in which is a filament 3S, one end of which is connected to the inside of can 29, and the other end of which is connected to a contact button 3l extending through a fiber disc 32 in the outer end of can 29 and contacting the inner end of the bullet.

A branch wire 33 connects conductor i8 to the bullet. Spaced from the junction of wire 33 and wire I8 is a second junction `between wire I3 and another wire 3@ which is connected to an insulatingvpost 35 Acarried by the outer annular face of plug 20. Arranged diametrically opposite to post 3&5 is a conductive post 36, and between these posts is a strip 3l of conducting material so arranged as to be ruptured when the bullet discharges.

Between the two aforesaid junctions in line It l is a resistor 38 which is generally selected to be A gun-barrel ll is suspended in the borehole on av cable 5 which passes over a sheave S at the Y surface to a drum l mounted on suitable trunsubstantially equal to the resistance of wire 33 plus the bullet, Aplus iilament 3G. The circuit, including wire I8, is grounded on the low side of resistance 3d. Resistance 3i?, can have a higher value, but it will serve its purpose when it has the aforesaid value, and, at the same time, re-

ground wire 3l which may be constructed o! small diameter insulated vWire or with a weak point where it connects to binding post 35, so that the gap in the wire will be large compared to the diameter oi' the wire and will eliminate any possibility of its severed ends coming together again. It is to be noted that until the `uppermost bullet is tired the applied current cannot get to the subsequent bullets, at least not in amounts suilicient to discharge them.

'I'he iiring arrangement of the present invention has been described above with reference to the use of direct current. In some respects, a1- ternating current may be more desirable since it permits the use of a stepdown transformer in the gun itself, thus minimizing the eiIect of cable leakage and providing much better voltage control on the iiring elements. In using alternating current the preferred embodiment is to alter the circuit shown in Fig. 3 by substituting a source of alternating current for battery Hfshifting 'the switch I4 to a position between the source of current and the gun, and inserting a step-down transformer in cable 9. t

It will be understood that the above'described specific embodiment of the present invention is submitted purely for illustrative purposes. Variouschanges in size, shape and arrangement of parts are contemplated within the scope of the present invention which is dened by the appended claims in which it is intended to claim this invention as broadly as the prior art permits.

I claim:

1. A perforating gun for boreholes comprising a gun body, bullets mounted for radial discharge from said gun body, a powder chamber arranged behind .each bullet, a firing filament in each of said outer chambers, and a firing circuit includ ing a .source of power, a. conductor connecting said source of power to each oi said filaments,

As previously stated, the bullet in discharging will rupture the A 2,296,318 duces the amount the voltage has to be increased a resistance arranged/ln parallel with each of said filaments, there being a separate resistance for each iilament, and a conductor independent o1' said filaments for connecting each oi.' said resistances separately and individually to the ground. Y

2. A perforating gun, according to claim 1, in which the ground connection for each'resistance comprises a conductor arranged to be ruptured by the discharge of the bullet.

3. A perforating guncomprising a gun barrel, a spiral groove in the surface of said barrel. a conductor laid in said groove, means for connecting said conductor to a source of power, wells arranged in said gun barrel at spaced intervals alongY said groove and spaced therefrom, a bullet in e'ach of said wells, a powder chamber behind each of said bullets, a :tiring nlament in each 'of said chambers, a resistance arranged in said conductor adjacent each of said wells, and an electrical connectionY between each of said illaments and the high side of its adjacent resistance.

4. A gun periorator, according to claim 3, in which a conductor is arranged across each well in such a manner asta be ruptured by the discharge of the corresponding bullet, having one vbehind each bullet, anelectrical iiring means in each of said powder chambers, and a firing circuit, including a source o1' power, a conductor connecting said source: of power to each of said ring means, a resistance arranged in parallel vwith each of said ring means, there being a separate resistance for each iiring means, and a conductor independent of said ring means for connecting each of said resistances to the ground separately and individually.

6. In a perforating gun for bore holes provided with a well, a bullet in said well, a powder chamber behind said bullet provided with an electrical firing means, and a ring circuit connected to said firing means, in combination, a resistance connected in parallel with said firing means, and an electrical conductor connecting saidre`sistance to a ground, said conductor being arranged to be ruptured when the bullet is discharged.

ROBERT R. THOMPSON. 

